Field of the Invention
The present invention relates to a measurement method, a measurement apparatus, a lithography apparatus, and a method of manufacturing an article.
Description of the Related Art
An exposure apparatus which projects a reticle pattern on a substrate such as a wafer via a projection optical system and transfers the pattern is used as a lithography apparatus which manufactures a device such as a semiconductor device, a liquid crystal display device, a thin-film magnetic head, or the like. In general, such an exposure apparatus detects a notch which is provided in a substrate conveyed into the apparatus and corrects a substrate position relative to the notch on a pre-alignment stage before sending the substrate to a substrate stage. This makes it possible to position an alignment mark which is provided on the substrate held by the substrate stage within the field of view of an alignment scope when the substrate is sent from the pre-alignment stage to the substrate stage.
On the other hand, for example, on a reconstruction substrate in FOWLP (Fan Out Wafer-Level-Packaging) or the like in which individual chips are arranged in the substrate, an error (θ error) is often included at a θ (rotational direction) position between the notch and the average lattice of the chips. Note that the average lattice is an average line defined on the boundary (between the chips) of the chips (pattern regions) from the arrangement of the chips on the substrate and is also called a scribe line. In this case, even if the substrate position is corrected relative to the notch, the alignment mark provided on the substrate may fall outside the field of view of the alignment scope when the substrate is sent from the pre-alignment stage to the substrate stage.
It can be also considered that the field of view of the alignment scope is expanded to bring the alignment mark into the field of view. Even if the alignment mark can be detected, however, the stroke of the substrate stage in the rotational direction may lack when the rotational amount of the substrate is large. In this case, the substrate has to be detached from the substrate stage and sent to the substrate stage again, generating a time for transferring the substrate.
To cope with this, Japanese Patent Laid-Open No. 63-104349 proposes a technique of detecting a scribe line after detecting a notch, obtaining a θ error in the average lattice of chips with respect to the notch from that result, and rotating a substrate on a pre-alignment stage based on the θ error (correcting a θ position). However, the position of the scribe line to be detected changes depending on the shapes or arrangement of the chips. Therefore, the field of view of a scope for detecting the scribe line needs to be expanded in order to handle various substrates.
Wide-area illumination such as bar illumination is needed in order to detect the scribe line accurately in a wide field of view. In such illumination, it is known that illumination light for illuminating the scribe line has an area equal to or larger than a detection region (field of view) on the substrate. Light, out of illumination light, which illuminates a region other than the detection region on the substrate is reflected by the region, becomes stray light by being further reflected by a peripheral structure or the like, and causes a detection error by entering a scope. Therefore, Japanese Patent Laid-Open No. 2006-41387 proposes a technique of reducing the influence of the detection error caused by such stray light.
In the technique disclosed in Japanese Patent Laid-Open No. 2006-41387, a representative corrected image for capturing a non-mark region different from a mark region on an object in which a mark has been formed and removes the stray light is obtained (prepared) in advance. In practice, however, the influence (appearance) of the stray light changes for each difference in material (reflectance) of the substrate or orientation of the substrate held by the stage, making it impossible to reduce the influence of the stray light sufficiently in the representative corrected image obtained in advance. It is possible to reduce the influence of the stray light by obtaining the corrected image for each lot or for each substrate. Considering a time required to obtain the corrected images, however, it is not realistic from the viewpoint of throughput.